The Photospheric and Helioseismic imager (PHI) on board of the ESA mission Solar Orbiter, to be launched in 2017, will provide measurements with high polarimetric accuracy of the photospheric solar magnetic field at high solar latitudes. The needed pointing precision requires an image stabilisation (ISS) to compensate for spacecraft jitter. The image stabilisation system works as a correlation tracker with a high-speed camera and a fast steerable mirror. The opto-mechanical and electronic design of the system will be presented.

This paper describes the wave-front correction system developed for the Sunrise balloon telescope, and provides information about its in-flight performance. For the correction of low-order aberrations, a Correlating Wave-Front Sensor (CWS) was used. It consisted of a six-element Shack-Hartmann wave-front sensor (WFS), a fast tip-tilt mirror for the compensation of image motion, and an active telescope secondary mirror for focus correction. The CWS delivered a stabilized image with a precision of 0.04 arcsec (rms), whenever the coarse pointing was better than 90 arcsec peak-to-peak. The automatic focus adjustment maintained a focus stability of 0.01 waves in the focal plane of the CWS. During the 5.5 day flight, good image quality and stability was achieved during 33 hours, containing 45 sequences that lasted between 10 and 45 minutes.

We describe the design of the Sunrise Filter Imager (SuFI) and the Image Stabilization and Light Distribution (ISLiD) unit onboard the Sunrise balloon borne solar observatory. This contribution provides the necessary information which is relevant to understand the instruments' working principles, the relevant technical data, and the necessary information about calibration issues directly related to the science data.

This paper describes the flight control software of the wave-front correction system that flew on the 2009 science flight of the Sunrise balloon telescope. The software discussed here allowed fully automated operations of the wave-front sensor, communications with the adaptive optics sub-system, the pointing system, the instrument control unit and the main telescope controller. The software was developed using modern object oriented analysis and design techniques, and consists of roughly 13.000 lines of C++ code not counting code written for the on-board communication layer. The software operated error free during the 5.5 day flight.

The testbed of the MCAO for the new 1.5 meter solar telescope GREGOR is now operational. Most of the components will be moved to the telescope after commissioning. The testbed features 4 adaptive mirrors (1 tip-tilt, and 3 DMs), and two Hartmann-Shack sensor units for wavefront tomography in a guide-region oriented approach. First system characteristics gained from setting up operation of the testbed are presented. We also comment on the effect of high-altitude deformable mirrors on subaperture alignment, and misregistration. We conclude that on-axis wavefront sensors should not be located behind high-altitude deformable mirrors. Furthermore, we present a general opto-geometric characteristic of micro-lens arrays needed for a Hartmann-Shack sensor which shall be used for extended fields of view - be it solar surface or laser guide stars, for example. This characteristic can be useful to have custom-made arrays manufactured for reasonable prices.

The 1m balloon-borne solar telescope Sunrise will be equipped with a wave-front sensing system for automatic in-flight focusing and alignment of the telescope and for high-precision image tracking. A six-element wavefront sensor measures low order aberrations of the telescope, including defocus and coma. The correction is achieved by moving the focusing mirror and the telescope secondary, respectively, in a closed-loop circuit. The same system measures image motion. The instrument requirements for the tracking are a dynamical range of about 30 Hz and a precision of about 0.005 arcs in the sky. The image motion signal feeds a closed-loop control system that drives both the tip-tilt mirror assembly and the mirrors that are needed for focusing and alignment. The tip-tilt unit is a dual-stage system, built at the Kiepenheuer-Insitut, consisting of a slow component with a large range of about 60 arcs and a fast component with a short range and high bandwidth. A breadboard-version of the Correlating Wavefront Sensor has been successfully tested at the German Vacuum Tower Telescope on Tenerife in summer of 2005. A closed-loop bandwidth of 80 Hz was measured for the tracking system. The wave-front sensor detected image aberrations pre-set by the telescope's adaptive optics system with the required accuracy. Sunrise will be flown in long duration stratospheric balloon flights, with a first scientific flight in 2009.